1. Technical Field
The present invention relates to a method of manufacturing a substrate, a substrate, a device provided with a substrate, and a determining method.
2. Related Art
Conventionally, in connecting a substrate to an electronic component such as a semiconductor chip, a solder is disposed on a substrate surface, whereby the substrate and the semiconductor chip are connected with each other via the solder.
On the other hand, in recent years, a lead-free solder is used as the solder in addition to a lead-containing solder. In accordance with the kind or the like of the device that is mounted on the substrate or the like, a lead-containing solder and a lead-free solder are distinguished to be used. For this reason, it is necessary to determine the kind of solder that is formed on the substrate.
There is a method of confirming the kind of solder by using a fluorescent X-ray; however, this method requires time and labor, and it will be difficult to produce a substrate efficiently.
Thus, a method disclosed in Japanese Patent Application Laid-open (JP-A) No. 2003-209349 is proposed for example.
By this method, a determination land is provided on a substrate surface, and the kind of solder is determined by the spread and protuberance of the solder to this determination land.
When a lead-free solder is used, the decrease in the surface tension is small at the time of heating and melting for reflowing, and the wettability to the determination land is inferior. For this reason, it is assumed that the solder will be thick at the central part to be raised gently.
On the other hand, when a lead-containing solder is used, the surface tension decreases at the time of heating and melting for reflowing, and the wettability to the determination land is good. For this reason, it is assumed that the solder has a flat shape having a uniform thickness.
In JP-A No. 2003-209349, it is assumed that the kind of solder can be determined by the difference in the surface tension at the time of reflowing. However, depending on the kind of lead-free solder or the melting temperature of the lead-free solder, the wettability to the determination land will be good even if a lead-free solder is used, so that the shape of the solder may have a flat shape having a uniform thickness in the same manner as the case of a lead-containing solder.
Therefore, it may be difficult to determine the kind of solder by the technique of JP-A No. 2003-209349.
As a result of studies made by the present inventors, it is found that, whether the solder is a lead-containing solder or a lead-free solder can be determined by the presence or absence of the luster on the solder surface, and can be determined by observing an outer appearance. Generally, a lead-free solder does not have a luster on the surface, whereas a lead-containing solder has a luster on the surface.
However, the solder formed on the substrate surface may be subjected to surface flattening (a coining treatment) because an electronic component such as a semiconductor chip may be disposed on this solder. The coining treatment is carried out by pressing the flat surface of a coining tool onto the solder surface, whereby the solder surface is flattened.
When the solder surface is subjected to a coining treatment in this manner, the solder surface may be damaged, and it will be difficult to determine the kind of solder by the outer appearance of the solder.